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Make Any Home Appliance Into a Solar Electric Hybrid 



MakejProjects 



Make Any Home Appliance Into 
a Solar Electric Hybrid 

Written By: Jason Poel Smith 



TOOLS: 

Soldering iron (1) 
Wire stripper/crimper (1) 
power drill and bit set (1) 
screwdriver set (1) 



SUMMARY 

Here is a video summarizing the project 



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Make Any Home Appliance Into a Solar Electric Hybrid 
Step 1 — Introduction 



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Make Any Home Appliance Into a Solar Electric Hybrid 




• This project is a simple and cheap 
way to integrate renewable energy 
into your home by turning your 
appliances into solar electric 
hybrids. 

• Here is how it works. A solar panel 
charges a storage battery. A 
control circuit monitors the 
battery's voltage. When the battery 
is fully charged, the circuit 
automatically turns on a power 
inverter and switches the appliance 
from running on grid power to 
running on the energy stored in the 
battery. 

• Then when the battery's voltage 
drops too low, the circuit 
automatically switches the 
appliance back to grid power until 
the battery is recharged. 

• This design doesn't require any 
modification to the appliance or 
your home's electrical system. It 
can work with any power source 
that is capable of charging a 12V 
battery (examples: wind turbines, 
bike generators, etc.). 

• But most importantly the system is 
scalable. This design is set up for 
outputs of up to 75 watts, but by 
swapping out parts for ones with 
higher power ratings you can power 
larger appliances or multiple 
smaller appliances at the same 
time. This lets you build a system 



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Make Any Home Appliance Into a Solar Electric Hybrid 



that fits your energy needs and 
your budget. 



Step 2 — System Overview 




• Here are the five basic parts of this 
system: 1. 12V Solar Panel (or 
other renewable power source) 2. 
12V Rechargeable Battery 3. 
Control Circuit 4. 12V Power 
Inverter 5. Automatic Switching 
Circuit 

• When assembled, the solar panel, 
battery, and inverter plug into the 
control circuit. The automatic 
switching circuit plugs into the 
inverter and the wall outlet. Then 
the appliance plugs into the 
automatic switching circuit. 

• The solar panel, battery, and 
inverter may be purchased off-the- 
shelf from a variety of locations. 
The last two parts of the system 
(the control circuit and the 
automatic switching circuit) will 
need to be constructed. This is 
detailed in later steps. 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 3 — Choose a Solar Panel 




• The solar panel that I used was a 5 watt model from Harbor Freight. The only difference 
that the power output makes is how quickly the battery will charge and how often the 
system will be activated. The only guideline to follow is that you don't want a panel that 
produces more power than you will use in a day. This would result in wasted energy. 

• Keep in mind that other power sources can be used in place of the solar panel. Wind and 
bicycle generator could also work well. They just have to be capable of charging a 12 volt 
battery. 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 4 — Choose a Battery 



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• When selecting a battery you have 
some trade-offs to consider. 
Batteries are more efficient and 
last longer when they are charged 
and discharged slowly. It is also 
best to minimize how deeply you 
discharge the battery. 

• As a result, bigger batteries will 
give better performance. But larger 
batteries are more expensive and 
take up more space. Deep cycle 
batteries are better at withstanding 
the regular charging and 
discharging experienced as part of 
a solar electrical system. But deep 
cycle batteries are also more 
expensive. 

• I am using a 7Ah battery to power a 
13 watt CFL lamp for my finch 
aviary. This seems to work well. If 
you are confused about which 
battery to buy, it might help to 
consult the battery expert at your 
local store. They should be able to 
recommend a battery for your 
application and budget. 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 5 — Choose a Power Inverter 





• The power inverter converts the output of your 12V DC battery into 120V AC that can 
power home electronics. I am using an 80 watt model from Harbor Freight. The most 
important requirement for your power inverter is that it must be capable of continuously 
powering the appliance(s) that you want to run. 

• Inverters generally list their maximum power ratings in terms of both continuous and peak 
watts. Generally you want to stay a bit under the continuous limit to avoid excessive 
heating. 



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Make Any Home Appliance Into a Solar Electric Hybrid 
Step 6 — Control Circuit Materials 




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Make Any Home Appliance Into a Solar Electric Hybrid 

• Printed Circuit Board (Radio Shack #276-170) 2 x Diode (Radio Shack #276-1 103) +5V 
Fixed-Voltage Regulator (Radio Shack #276-1770) 555 timer IC (Radio Shack # 276-1723) 
MPS2222A NPN Transistor (Radio Shack #276-2009) IRF510 MOSFET (Radio Shack # 
276-2072) 

• 100uF 15V Capacitor (optional) 2 x 0.1 uF 15V Capacitor (optional) 2 x 10K-Ohm 15-Turn 
Cermet Potentiometer/Trimmer (Radio Shack #271-343) 100-Ohm Resistor (Radio Shack 
#271-005) 330-Ohm Resistor (Radio Shack #271-012) 1K-Ohm Resistor (Radio Shack 
#271-004) 12VDC/125VAC 10A SPDT Mini Relay (Radio Shack #275-248) 

• 12VDC Vehicle Power Accessory Outlet (Radio Shack #270-046) Project Enclosure 
(6x3x2") (Radio Shack #270-1805) 2 x bolts (1/4" or smaller) 2 x nuts (1/4" or smaller) 2 x 
1/4" Fully Insulated Female Quick Disconnects (Radio Shack #64-3133) 2 ft. x 16 guage 
wire Jumper Wires 

• Part Substitutions: I chose these parts because they are easily accessible (most can be 
purchased from Radio Shack). However, all of them may be substituted for other parts 
with similar values. You can generally find them cheaper online. 

• The trimmer potentiometers may be replaced with single turn potentiometers or fixed value 
resistors. I chose these potentiometers because it is easier to make fine adjustments 
when calibrating the circuit. The input diode can be replaced with a schottky diode for 
better performance. 

• Optional Charge Controller Materials: Diode (Radio Shack #276-1103) 555 timer IC (Radio 
Shack # 276-1723) 0.1 uF 15V Capacitor (optional) MPS2222A NPN Transistor (Radio 
Shack #276-2009) IRF510 MOSFET (Radio Shack # 276-2072) 

• Optional Charge Controller Materials cont.: 2 x 10K-Ohm 15-Turn Cermet 
Potentiometer/Trimmer (Radio Shack #271-343) 100-Ohm Resistor (Radio Shack #271- 
005) 330-Ohm Resistor (Radio Shack #271-012) 1K-Ohm Resistor (Radio Shack #271- 
004) 12VDC/125VAC 10A SPDT Mini Relay (Radio Shack #275-248) 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 7 — Control Circuit Design 



Control Circuit 



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Make Any Home Appliance Into a Solar Electric Hybrid 

• This circuit is a modified version of a charge controller circuit that was designed by Mike 
Davis ( http://www.mdpub.com/555Controller/index... ). 

• In the original circuit, a 555 timer IC was used to disconnect a battery from the solar panel 
when its voltage gets too high (to prevent it from over charging). In my design, the control 
circuit connects the battery to an inverter and an output circuit when the battery is fully 
charged. 

• Here is a brief description of how the circuit works. A 5V voltage regulator powers the 555 
timer IC and sets its internal reference voltages. A pair of potentiometers (variable 
resistors) are set up as voltage dividers that provide a signal to the timer IC that is 
proportional to the battery's voltage. 

• These signals determine the operating range of the system. As the battery's voltage rises 
and falls, so does the output signals of the potentiometers. When the signal at pin 6 rises 
above 3.3V, the output of the IC goes LOW and activates the relay through a series of 
transistors. 

• When the signal at pin 2 falls below 1 .6V, the output of the IC goes HIGH, which 
deactivates the relay. By setting the positions of the potentiometers, you determine at what 
voltages the battery must be to activate and deactivate the output. 

• Alternate Design with Charge Controller A charge controller usually isn't required for this 
setup. If the output of your solar panel is small relative to the storage capacity of your 
battery and you are powering a device that is frequently turned on, then you generally don't 
need to be worried about over charging the battery. 

• However, if you wish to use a charge controller, you may attach one between the solar 
panel and the control circuit. I have also provided an alternate circuit design that includes 
a charge controller built into the control circuit. 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 8 — Preset the Potentiometers 





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• Before assembling the circuit, it is a good idea to preset the potentiometers. This will 
prevent a lot of troubleshooting later. As indicated in the pictures, the values of the 
potentiometers should be set to the following: 

• Basic Control Circuit Design Potentiometer connected to pin 2: 8600Q between wiper and 
the positive rail, and 1400Q between wiper and the negative rail. Potentiometer connected 
to pin 6: 7200Q between wiper and the positive rail, and 2800Q between wiper and the 
negative rail. 

• Optional Charge Controller Potentiometer connected to pin 2: 8700Q between wiper and 
the positive rail, and 1300Q between wiper and the negative rail. Potentiometer connected 
to pin 6: 7500Q between wiper and the positive rail, and 2500Q between wiper and the 
negative rail. 

• These will not be the final calibrated values. These are just convenient starting locations to 
get you in the ball park. The final settings will depend on the specific battery that you are 
using and its recommended operating range. 

• When making the final adjustments, it is helpful to use a power supply with an adjustable 
voltage regulator such as a LM317T (Radio Shack #276-1778). See the following step for 
an example. If you don't have access to an adjustable power supply it will take a bit of time 
tweaking the values and checking it with a multimeter. 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 9 — Control Circuit Assembly 




• Always prototype circuits on a breadboard before soldering them onto a printed circuit 
board. In my breadboard prototype, I included an adjustable voltage regulator so that I 
could quickly simulate the charging and discharging cycles. This makes it convenient to 
work out the final adjustments to the potentiometers. 

• If you are using the same boards that I am, you can just copy my layout. The PCB is a bit 
longer than it needs to be for this circuit. To trim off the excess, use a sharp knife to 
deeply score a line across the board through one column of holes and break it off along the 
line. 



Step 10 — Automatic Switching Circuit Materials 




• Automatic Switching Circuit 
Materials: Project Enclosure (Radio 
Shack #270-1801) 125VAC/10A 
DPDT Plug-In Relay (Radio Shack 
#275-217) 8 x 1/4" Fully Insulated 
Female Quick Disconnects (Radio 
Shack #64-3133) 1 full extension 
cord with male and female ends 1 
power cord with male end only 
(preferably a different color than 
the extension cord) 

• Tools: Wire Strippers Crimping 
Tool (for quick disconnects) Knife 
or Dremel (for cutting housing) 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 11 — Automatic Switching Circuit Design 








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• This circuit has only one major part: a double pole double throw relay. It is wired in such a 
way that it will automatically switch the output whenever the inverter is powered on. 

• To achieve this, the input line from the wall outlet is connected to the normally closed 
contacts and the output line going to the appliance is connected to the common contacts. 
Then the input line from the inverter is connected to both the coil and the normally open 
contacts. 

• When the device is inactive, your appliance will be connected to the wall outlet and 
powered by the grid as it normally would be. The only difference is that it is going through 
the relay. But when the device is activated, the inverter turns on and sends power to the 
normally open contacts and the coil. 

• This switches the relay. The appliance is disconnected from the wall outlet and connected 
to the inverter. This is how the switching circuit will automatically switch to your renewable 
power source whenever it is available. 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 12 — Automatic Switching Circuit Assembly 




• Begin by cutting the extension cord into two pieces. The female end will be the output line 
where the appliance is plugged in. The male end will be the grid input line that is plugged 
into the wall outlet. The second power cord will be the input line that is plugged into the 
inverter. 

• You may wish to select a power cord for the inverter line that is a different color than the 
other cords. This helps prevent mixing up the lines. You may also want to label them. 

• Cut a 3 inch section off the end of the inverter power cord. This will be the jumper between 
the coil contacts and the normally open contacts on the relay. Strip 1/2 inch of insulation 
from the ends of all the wires. 

• Twist together the exposed ends of the inverter cord and the 3 inch section that you just 
made and crimp them into a single pair of quick disconnects as shown in the picture. Then 
crimp quick disconnects onto all the remaining wire ends. Connect the output line (female 
end of the extension cord) to the common terminals. 

• Connect the grid input line (male end of the extension cord) to the normally closed 
terminals. Lastly, connect the first set of quick disconnects on the inverter input line to the 
coil terminals and connect the second pair quick disconnects to the normally open 
terminals. 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 13 — Project Housing Modifications 



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• Solar Panel Attachment Point The cables from my solar panel have clamps on the end. So 
I decided to use bolts as the attachment points on the control circuit housing. For this, I 
found a pair of bolts and nuts that fit the clamps. 

• Then I drilled holes in the side of the housing that were a little smaller than the bolts and 
screwed the bolts into the holes. The nuts were threaded onto the bolt inside the housing. 
This will make the attachment point for the wires inside the housing. 

• Holes for Wires Because so many quick disconnects are used, it would be inconvenient to 
feed the wires into the enclosures through drilled holes. Instead, I found it easier to just cut 
small slits in the side of the enclosure where the two halves come together. Do this for all 
the wires that go through the walls of the enclosures. 

• DC Power Outlet Hole Drill or cut a 1 3/32" hole in the side of the housing for the control 
circuit. Since this is an odd size, you will probably have to drill a 1" hole and widen the 
hole with a file or knife. Insert the DC power outlet into the hole. If it doesn't fit tightly, you 
can secure it in place with glue. 



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Make Any Home Appliance Into a Solar Electric Hybrid 

Step 14 — Optional Testing With a DC Power Supply 



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Make Any Home Appliance Into a Solar Electric Hybrid 




• Since a system that is solar 
powered is most active in the 
middle of the day (when many 
people are at work), it can be 
inconvenient to do initial testing 
and observation of the system at 
work. To get around this, you may 
wish to use a DC power supply in 
place of the solar panel for initial 
testing. 

• The simplest and cheapest way to 
do this is to use an DC power 
adapter. Find one that has a 
operating voltage of about 12V. The 
open circuit voltage (no load) will 
usually be a good bit higher. The 
exact type doesn't matter. You 
probably have a suitable DC power 
adapter lying around your house 
somewhere. 

• You may wish to add a capacitor 
between the positive and negative 
terminals if the power supply 
doesn't have a steady output. 
Connect the positive wire from the 
power supply to the positive 
terminal of the control circuit and 
the negative wire to the negative 
terminal of the control circuit. 

• This will charge the battery and 
fuction just as the panel would, but 
isn't dependent on sunlight. This 
can make it more convenient to 
montior performance and trouble 
shoot the initial setup. 



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Make Any Home Appliance Into a Solar Electric Hybrid 



Step 15 — Finished Assembly 





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• Be sure to test all parts of the system individually before assembling them together. 

• Attach the clamps from the solar panel onto the bolts on the control circuit housing. Then 
attach the input wires on the control circuit board to the bolts on the inside the housing and 
tighten the nuts to hold them in place. Attach the battery lines on the control circuit to the 
corresponding battery terminals. 

• Be careful not to mix up the positive and negative wires! You probabably want to label 
them or color code them. Attach the output lines on the control circuit to the DC power 
outlet. Be sure to attach the positive wire to the center pin and the negative wire to the 
outer barrel. Once everything is in place, close up the housing. 

• Attach the inverter by plugging it into the DC power outlet. Put the automatic switching 
circuit into its housing and close it up. Then plug the inverter power cord into the inverter. 
Plug the appliance into the output line. If the battery was fully charged, the appliance 
should be powered. Lastly plug the wall outlet power cord into a wall outlet. 

• Carefully observe all the parts of the system to make sure that nothing is making any 
weird sounds, smells, or is catching on fire. If not, you have a functioning solar electric 
hybrid adapter. 



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Make Any Home Appliance Into a Solar Electric Hybrid 

Step 16 — Final Notes and Future Design Improvements 



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• Final Notes and Warnings: The 
operation of this device involves 
regularly cutting power and 
switching to a second power 
source that may be out of phase. 
As a result, the output may 
momentarily fluctuate. This is 
especially true if your switching 
circuit uses a relay with a low 
activation voltage. 

• In this case, the relay might switch 
before the inverter is running at full 
power. This momentary fluctuation 
is no problem for simple appliances 
like a lamp or fan, but may 
potentially cause problems for 
sensitive electronics. So choose 
your appliances carefully. I am not 
responsible if you fry your 
computer. 

• Future Design Improvements: The 
biggest problem with this design is 
that the device activates as soon 
as the battery is fully charged. This 
does not necessarily coincide with 
when the appliance is turned on. 
Even if no appliance is on, the 
relays and the inverter will still 
consume power. 

• In a future design, I will combine 
the various parts of this project into 
a single unit that has a sensor to 
determine when the appliance is 
turned on. Only once the appliance 
is turned on will the control circuit 
activate the relays and the inverter. 

Page 21 of 22 



Make Any Home Appliance Into a Solar Electric Hybrid 



This will help ensure that less 
power is wasted. 

• I would also like to add something 
to the circuit to smooth the output 
of the system to avoid the power 
fluctuations mentioned above. This 
might be something as simple as 
adding a time delay on the 
switching circuit. 

• If you have any suggestions for 
improvements please leave a 
comment and let me know. 



This project is a cheap way to integrate solar power into your home. 

last generated on 2012-10-31 01:40:14 AM. 



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